Mole Fraction

What is this formula?

Mole fraction expresses the proportion of a component relative to the total amount of substance present in a mixture. It is a dimensionless quantity and is widely used in solution chemistry, thermodynamics, and gas mixtures.

When to use it

Use this formula when analyzing the composition of mixtures, applying Raoult's law, calculating partial pressures, performing vapor-liquid equilibrium calculations, or describing multicomponent systems.

Example

A gas mixture contains:

Nitrogen: 3.0 mol

Oxygen: 1.0 mol

Data:

ni = 1.0 mol

ntot = 3.0 + 1.0 = 4.0 mol

Formula:

xi = ni/ntot

Substitution:

xi = 1.0/4.0

Result:

xi = 0.25

The mole fraction of oxygen is 0.25.

Applications

- Gas mixture analysis

- Solution chemistry

- Raoult's law calculations

- Partial pressure calculations

- Chemical thermodynamics

- Phase equilibrium calculations